If the carbon dioxide concentration of the atmosphere is to be stabilized, one must capture and store carbon dioxide from all types of power plants. Natural gas-fired turbines and other dilute sources should not be exempt from carbon dioxide capture and storage. It is simply not sufficient to collect carbon dioxide only from coal fired power plants. Unfortunately, collecting carbon dioxide from low concentrations in the gas stream, requires a strong sorbent that is typically expensive to regenerate. This already poses a problem for conventional flue gas scrubbing in a coal-fired power plant.
Even though the initial concentration of carbon dioxide in the flue gas of a coal fired power plant is well above ten percent, a thorough scrubber will have to drive the carbon dioxide concentration well below one percent. However, it is difficult for sorbent-based flue-gas scrubbers to capture more than 80 to 90 percent of the carbon dioxide produced. This is not good enough to achieve the 80 percent economy-wide reduction in carbon dioxide emissions that will be necessary over the next few decades. Extraction from more dilute sources and lowering the residual carbon dioxide concentrations released at coal-fired power plants are required to increase the overall amount of carbon dioxide captured.
Most of the research and development for capture technologies at large sources of carbon dioxide are focused on the high concentrations that are available at coal combustion plants. These limited concentrations range typically from ten to fifteen percent carbon dioxide by volume. Flue gas scrubbing of carbon dioxide is usually accomplished in a single step. However, in most designs there is a prior scrubbing stage to remove sulfur and other sour gases from the flue gas. This is necessary because most carbon dioxide sorbents are irreversibly fouled by sulfites and sulfates.